1. Field of the Invention
The present invention relates to a control method/system for controlling shifting in an at least partially automated mechanical transmission system. In particular, the present invention relates to the control of shifting in a vehicular automated mechanical transmission system wherein the system senses conditions indicative of a shift from a currently engaged gear ratio (GR) and evaluates, in sequence, the desirability of skip shifts and then single shifts and commands shifts deemed desirable.
More particularly, the present invention relates to control logic for exaluating shift feasibility and target gear identity in view of built-in engine response delays provided to assure proper engine brake deactivation.
2. Description of the Prior Art
Fully or partially automated mechanical transmission systems for vehicular use are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,648,290; 4,722,248; 4,850,236; 5,389,053; 5,487,004; 5,435,212 and 5,755,639. The use of engine brakes (also known as compression brakes, exhaust brakes or Jake brakes) and transmission controls utilizing same are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,409,432 and 5,425,689, the disclosures of which are incorporated herein by reference.
Controls for automated mechanical transmission systems, especially wherein shifting is accomplished while maintaining the master clutch engaged, wherein single and/or skip shift feasibility is evaluated are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,576,065; 4,916,979; 5,335,566; 5,425,689; 5,272,939; 5,479,345; 5,533,946; 5,582,069; 5,620,392; 5,489,247; 5,490,063 and 5,509,867, the disclosures of which are incorporated herein by reference.
It is also known that manufacturers of diesel engines for heavy-duty trucks, such as Caterpillar, Cummins, Detroit Diesel, etc., build in a response delay in their electronically controlled engines to allow proper engine brake deactivation. This is done to prevent fueling of the engine if the brake is still active which might cause valve and/or engine damage. This delay typically varies (from about 100 ms to about 500 ms) depending on the type of engine and/or engine brake.
The control of the present invention provides an improved control for a vehicular automated mechanical transmission system which will sense conditions indicative of shifting from a currently engaged gear ratio, and will evaluate, in sequence, the desirability of large skip shifts, then single skip shifts, and then single shifts, and will command a shift to the first target ratio deemed to be desirable under current vehicle operating conditions.
In a preferred embodiment of the present invention, by setting (i) a maximum acceptable shift time for completing upshifts and (ii) upshift feasibility rules to determine if a proposed shift is feasible under current vehicle operating conditions. The shift feasibility rules comprise a two-part test, (a) can the upshift be completed above a minimum engine speed? and (b) when completed, will the engine, in the target ratio, provide sufficient torque at the drive wheels to allow at least a minimum vehicle acceleration?
The present invention, determines the upshift brake deactivation delay provided for a particular engine and evaluates possible target gear ratios based upon the delay.
The above is accomplished by determining that shifts initiated with the engine brake active (typically only coasting downshifts) and engine brake aided upshifts will take a longer time to complete due to the built in engine brake deactivation delay.
Accordingly, an improved shift control for automated mechanical transmissions is provided which will automatically evaluate and command desirable skip and then single shifts.
This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.